knudson



2 Sheets-Sheet l. I

O S D U N K A A M M m ELEGTRO ACOUSTIC APPARATUS.

PatentdMar. 29, 1887.

g Q (Fwd/41 N, PETERS. Phulo-Lilhogmphcr, Washington, D: C.

(No Model.) -2 'Sheets-Sheet 2.

' A. A. KNUDSON. ELEOTRO AGOUSTIGAPPARATUS.

No. 360,308. r Patented Mar. 29, 1887.

N. PETERSv PhotuLilhagnpher, Wnhingmn, D. C.

UNITED STATES PATENT OFFICE.

ADOLPHUS A. KNUDSON, OF BROOKLYN, NE\V YORK.

ELECTRO-ACOUSTIC APPARATUS.

SPECIFICATION forming part of Letters Patent No. 360,308, dated March29. .887 Application filed Tune 15, 1886. Serial No. 205,189. (Nomodel.)

To aZZ whom it may concern:

Be it known that I, ADOLPHUS A. K'NUD- soN, a citizen of the UnitedStates, residing in Brooklyn, in the county of Kings and State of NewYork, have invented certain new and useful. Improvements inElectro-Acoustic Apparatus, of which the following is a specification.

The object of myinvention is to provide an apparatus whereby the soundsproduced by an electrical instrument when actuated by cu rrents of veryfeeble intensity may be rendered audible and the signals may beinterpreted, as in the case of telegraph-instrumentsworked onvery longlines or when there is great cseape of current, and whereby the use ofrelays and localbatteries may be generally dispensed with.

My invention'consists in the combination, with an electricalreceiving-instrument, of an acoustic apparatus, the latter being soconnected with the movable or operative parts of the former as tointensify the sounds produced, rendering them audible when otherwisethey would be entirely inappreciable; and my invention also consists inthe application to such receiving-instruments of a diaphragm orresonator of novel form and material.

In the accompanying drawings, which illustrate myinvention, Figure l isa side view, partly in section, of a telegraphic instrument. Fig. 2 is aplan View of the same, also partly in section. Fig. 3 is an elevation ofthe diaphragm; and Fig.4 is an end viewot' the'electro-magnet, showingarmature.

In the drawings, A represents an electromagnet; B, the yoke O, theangular brass support for the magnet, attached to the base D.

E is the standard for the adjusting device.

F is the case for the diaphragm or resona tor R. This case may be ofwood or similar material.

1G is an auxiliary piece attached to the case F and of the samematerial, adapted to receive the end of the ear-tube H.

The armature a of the electro-magnet A,with its lever a, is made aslight as possible, and its motion is limited in the usual manner by thestops a and a. The armature is held back by the spring 8, and propertension is given to the latter by means of the cog-wheel W,tangent-screw w, and milled wheel 10. As the cord attached to the spring8 winds around.

the arbor-of the wheel W, it will be seen that this device will enablethe operator to obtain a very delicate adjustment of the armature.

The armature a plays preferably in front of one core only of theelectro-magnet. The lower core in the drawings has the pole-piece Pattached to it by means of the screw 1). On the top of the pole-piece Pthe armature rests, and is kept in place by one or more small pinsextending from the lower end, which loosely enter corresponding holes inthe upper end of the pole-piece. These are shown in Fig. 4. Light spiralsprings s are attached to each side of the armature by the hooks s" andto the arbor of the small adjustingscrew p on the pole-piece 1?. Thesesprings hold the armature in position with a gentle pressure downward.

Z represents a metallic case, with which the electrical portions of theinstrument are pret'- erably covered. The forward and backward screws orstops, between which the end of the armature-lever a plays,are held bythe upright pieces a and a and these are supported by the piece a". Thepiece through whichthe back contact-screw passes, is attached directlyto a. The piece a, through which the front contact-screw passes, is heldby the two side pieces, a a Fig. 2. The piece a is supported by the twobars I) I), which diverge, as shown in Fig. 2, and are firmly attachedto the diaphragm by passing through the latter, the connection beingmade rigid by the nuts I) b on the inside and outside. Again, the bar I)has one end firmly attached to the lower end of the piece a, (whichholds the contactscrew (L2,) and the other end passes through the diaphragm, and is firmlyjoined to the latter at its center by the small nut72*. It will therefore be seen that by means of the bars b b and b', therectangular frame within which the armature-lever a plays, and whichcarries the contact or limiting stops a a", allthe parts which areaffected by the motion of the arma- 2o drawings, its ability to take-upand give off communicated to the wooden case, and hence all the sound isconfined to the resonator itself. Very faint sounds, therefore, causedby the motion of the armature and its impact against its stops arecommunicated to the resonator, and are capable of being heard at itsside opposite the magnet, where the ear may be directly applied, orwhere the tube H may be conveniently attached. This tube I prefer tohave of the usual flexible form, as such form accommodates any desirableposition of the operator.

It remains now to describe the diaphragm or resonator R. I make this ofthin aluminium. The qualities of lightness and electrical conductivityofthis metal are well known. Its resonance is also well understood; butI'have found thatwhen a very thin sheet is spun into a circular form,and especially when corrugations are formed in its sides, as shown inthe sounds is largely increased. Such adiaphragm increases to aconsiderable degree the sensitiveness and practical value of anyacoustic or telephonic instrument to which it may be applied.

The electro-acoustic lnstrument herein described has shown by actualexperiment that a current may give motion to thearmature, and Morsesignals be read thereby, while the needle of a sensitivegalvanometerinserted in the circuit will not be affected. The form ofmagnet, the means for delicate adjustment, the method of supportingthelimiting-stops from the resonator, and the nature ofthe resonatoritself all contribute to this result.

It will be obvious that the diaphragm may be stamped into the requiredshape as well as spun. Another quality which fits the metal alluded tofor the resonators for electrical and acoustic instruments of allkindsis that of resisting corrosion. It may be kept for any i lcngthoftime in a damp atmosphere, and rethinindeed for use as a, resonator.

hoop of brass, over which the aluminium disks or sides of the resonatorare drawn. This decreases the cost without afiecting the performance ofthe device.

Iclaim as my invention-- 1. The combination, substantially ashereinbefore set forth, of an electro-magnet, its armature andarmature-lever, limiting-stops therefor, a resonator or diaphragm ofaluminium from which said stops are supported, and means for adjustingthe said armature according to the attraction exerted uponit by saidelectro-magnet.

2. In an instrument adapted to receive and transmit sounds, a resonatoror diaphragm formed of two disks of aluminium secured to the edges of aring or hoop of different material and thicker than said disks.

3. The combination, substantially as hereinbefore set forth, with anelectro-magnet, of

a polepiece attached to one of the cores thereof,

an armature held against said pole-piece by springs or their.equivalents in such position as to face the other core of said magnet,limiting-stops for said armature, a diaphragm or resonator from whichsaid stops are supported, and means for adjusting said armatureaccording to the attraction exerted upon it by said electro-magnet.

4. The combination, substantially as hereinbefore set forth,with anelectrical receivinginst-rument,of a diaphragm or resonator whichsupports the stops limiting the movement of the armature of saidinstrument, said diaphragm consisting of two disks of aluminium withcorrugated surfaces secured to the edges of a ring or hoop of differentmaterial and thicker than said disks.

5. The combination, substantially as hereinbefore set forth, with anelectro-magnet, of a pole-piece attached to one of the cores thereof, anarmature resting upon said pole-piece and held in place by springs insuch position as to face the other core of said magnet, limitingstopsforsaid armature, and a diaphragm or resonator supporting said stops, saiddiaphragm consisting of two disks of aluminium secured to the edge of aring or hoop of different material and thicker than said disks.

, In testimony whereof I have hereunto sub scribed my name this 12th dayof June, A. D. 1886.

ADOLPHUS A. KNUDSON. T

Witnesses: I

DANL. \V. EDGECQMB, GHARLEs A. TERRY.

